Apparatus for producing and electromotive force of special wave form.



E. F. W. ALEXANDERSON.

APPARATUS FOR PRODUCING AN ELECTROMOTIVE FORCE OF SPECIAL WAVE FORM.

APPLICATION I'ILED AUG.22. 1914.

1,250,752. PatenbedDec. 18,1917."

JNYL'NTUH mar 17 Wanamsam 7&5 Arramz mrzvrsszs:

1 allgbhom it mag concern:

v UNITED STATES PATENT OFFICE.

ERNST law. ALEx'ANDEnsoN, or SCHENECTADY, NEW YORK, ASSIGNOR 'ro GENERAL ELECTRIC COMPANY, a CORPORATION or NEW YORK.

arrmarus FOB rnonocme an i'znaoraoivrorrva FORCE or SPECIAL wave roam.

AfNDEKSON, a citizen of the United States, re-

=' gsiding-at Schenectady, in the county of Schene'c'tady, State of New York, have invented certain new and useful Improvements in Apparatus for Producing an Electromotlv'e Force of Special W'ave Form, of which the following is a specification.

' My'invention relates to apparatus for produci'ng an electromotive force of special '1 wave iform. The object of my invention is to provide an improved apparatus for pro- .ducin'g an alternating electromotive force of unsymmetrical wav form. A further object of my invention is to provide an improved dynamo-electric machine adapted to gener- The features'of novelty which I consider patentably characteristic oi my invention are-definitely'indicated in the claims appended hereto. The principle of my invention and the construction of an apparatus embod ing the same will beunderstood from t e following description taken in connection with the accompanying drawings, in which: v

Figure 1 is a partial sectional elevation showingthe stator and rotor members of an apparatus embodying thenovel features of my invention; Flg. 2 is a sectional end elev tion of the apparatus shown in Fig. 1; and igs. 3 and 4: are explanatory diagrams. The convenient and accurate production of an electromotive force of a predeter inined special wave form is very desirable in certain fields of electrical engineering. A

particularinstance of the use of such a speclalwave form electromotive force is in the multi-party bell ringing devices for tel-erotatable commutator having a plurality of se ents operatively connected to a potentia rheostat in such a way that any desired potential, either positive, zero or negative, may be connected to any number of the segments', so that in one revolution of the com mutator the time during which diflerent qyoltages' should be applied, as .well as the magnitude of the voltage, may be propor- Specification of Letters Patent.

' Application filed August 22,1914: Serial No. 858,077.

Patented Dec. 18,1917.

tioned as necessary to prod'uce the desired,

wave form. In accordance with my present invention an electromotive force of practically any desired wave form may be dynamically produced in a" simple, accurate and efiicient' manner. It is thus possible, in accordance with my invention, to dynamically produce uns. mmetrical wave forms which are in effect ike the wave forms heretofore produced by the commutator methods,- and which are in every respect sufiiciently close approximations thereto for all practical. purposes. r

The principle of my present invention consists'in generating an elect-romotive force of a predetermined desired'wave shape by the use of an electric current-carrying coil.

interlinked' with a magnetic circuit, the reluctance of which is periodically varied by a rotating member, the shape of therotating member being such that the diflerential variation of the magnetic reluctance of the magnetic circuit is equal to the momentary value of the electromotive force of special vvave shape which it is desired to produce. In carrying out my invention '1 Jrovide a current-carrying coil interlinke with a.

magnetic circuit together with means v'vhereby the necessary change in the flux interlinked with the coil may be eifected to'produce the electromotive force of the special.

wav form. An elect-romotive force is generated in the current-carrying coil by the change in the total fluxinterlinked with the coil, and the differential of the change in the total flux interlinkage between the coil and the magnetic field is designed in accordance with my present invention to be substantially proportional to the instantaneous values of the 'electromot ive force of the desired special wave form.

My invention will be bcst'understood by reference first to Figs. 1. and 2 of the drawings, which illustrate an apparatus designed in accordance with the principle of my invention for producing analternating electromotive-force of special-wave form. The apparatus is in substance an inductor alternator having a stationary armature winding consisting of a single coil, a stationary exciting Wiiiding, and a rotatable -magnetic inductor. Th stator 5 of'the apparatus has on its inner eriphery two spaced slots 6 and 7. In tie particular machine illustrated the slots 6 and 7 embrace of-the .rylng a coil 8 in'the The two magnetic stator members are suitably spaced from one another and se- 'frame members 10 and 11 producing the radial \vldth a of thestator periphery. Acoil 8 is positioned in the slots and is able wedges 9. The free terminals of the coil 8 serve as the .source from which the alternating electromotive force of special wave form is taken. It will of course be understood that the stator may carry more than one coil,"and I have merely illustrated onecoil in the accompanying drawings for the purpose of explaining the principle of my invention.

eference to Fig: 2 of the drawings will show that themachine has duplicate stator parts. -That is, there are .two similar laminated magnetic stator members 5 each carspaced slots 6 and7.

cured in their, respective spaced positions by means of two annular magnetic frame members 10 and 11 and cooperating bolts 12. An exciting coil 13 is carried by the between two stator members 5, and is adapted to develop a magnetic field to which the conductors of the ,coils 8 are subjected.

e apparatus also has two.rotors or inductors 14, one cooperating'with each stator member 5. Each inductor consists -of a laminated magneticbody of special peripheral configuration suitably-keyed to a rotatably mounted shaft 15. The inductors are securely fastened together with a magnetic spacing member 16 thcrebetween by bolts 17. It will thusbe evident that the stator members 5 and the rotor members l-l constitute the magnetic circuit for the flux field to which the .coils 9 are subjected.

Each rotor 14 has a periphery of varying radial dimension, whereby the air gap between the stator and the rotor members is ununiform, so that rotation of the rotor varies in a predetermined way the reluctance of the magnetic circuit in the vicinity of the coil located in the slots 6 and 7.- Fig. 1 shows clearly the peculiar peripheral configuration of the rotor in the dynamo-electric machine which I have illustrated by way of example. to explain the principle of my invention. It. will he observed that the surface of the rotor is divided intothree sections, each section having a gradually varying radial width, Thus, the maximum than the minimum radial width I; of'this section, the maximumradial width r? of the adjacent section Y is greater than the minimum radial, width 1/ and the maximum ltb dial width-r ol' tlu: third section Z is greater than the minimum radial width f. It will be observed that the variation in radial width of each section, that is. the variation in width from a. lo I; of section X, from 0 old securely therein by suitrotor has 'a' .ratchet-likc wnpheral surface, whereby the and is positioned A, gradual,

dial width of the. sections themselvesis abrupt and of a much larger magnitude. The exciting coil 13 is energized by direct current, as "in an inductor alternator, passing through the air,

the rotors,

to the spegap is produced of the stator will vary as the rotor rotates. The flux will have during one revolution of the rotor in the direction of the arrow the form indicated by curve A in served that the flux curve is ma'de up of three sections 'of gradually decreasing flux the three sections 1 values,

corresponding to X, Y,

and Z of the rotor, two-relatively Fig. 3. It will be obabrupt points of fluii decrease, correspondf section X to section ing to the passagefrom to section Z, respec- Y and from section Y tively, of the rotor, and one abrupt point flux increase, corresponding to the pas-- to section X of the of sage from section Z rotor.

The electromotive force induced in. the

coil 8 is determined by the variatioriih the' total flux interlinked with the coil. If we call the flux interlinked in the slot. 7 flux interlinked with the conductors in the slot 6 the outgoing with. the conductors the incoming flux and the r flux, the'resultant electromotive force induced in the coil is determined by the difference between the -incoming and the outgoing fluxesllfhg dif; ference n the value of the incoming and outgoing fluxes can be shown to be to portlonal to the difi'erential of the total (luxvariation between the'slots6 and 7. If, therefore, we integrate the total fiux variation between the slots 6 and instantaneous vol age induced in the coil 8. The magnetic inductor is, therefore. shaped that the 7 and obtain the. differential of this integral the result w'll" be proportional to'tho ditt'ereutial of the variation of the magnetic I reluctance of the magnetic circuit of the the rotation of the insubstantially machine effected by ductor is momentary values of the electri'nnotive force suction X is greaterof special wave shape which it is desired to produce.

The calculated voltage at the terminals of the coil 8 when subjected to a flux variation of the character prodm-m'l by the rotation of an inductor of II proportional to the uronliguration heroin illustratvd is rr )resi-ntml by curve B of Fig. 3,

of the drawings. When the coil 8 occupies a position with rrsprrl to the llux wave as diagrammulir-ally iudiratrd at l in Fig. 3 of the drawings. tlu: conductors lorat'ed in' the slot 7 will be ruttiuj: a. magnetic field of maximum value, while the conductors loreaches the slot 7, whereupon the variation in the total flux interlinked with the coil the coil" When the coil 8 is in the position indicated at I in Fig. 3, the change in the total flux interlinked with the coil is large,

and the voltage induced in the coil is correspondingl'y large, as represented in the volta e curve B Just before the forward tip of section X of the rotor reaches the slot 6, the coil 8:.wil1 occupy a position with respect to the flux wave indicated at II in Fig.

' 3 of the drawings; An instant later the con ductors in the slots 6 are subjected to a magnetic field of maximum value and the change in the total flux interlinked with the coil is .now of a relatively small magnitude and-is furthermore opposite ineffect, so that a neg ative voltage of smalLmagnitude appears at the terminals 'of the coil 8. That this voltage is negativewill be apparent by observing that the outgoing flux is larger than, and hence dominates, tlie incoining flux. \Vhen the coil'S occupies the position indicated at I, the incoming flux is greater that the outgoing flux When the forward tip of section Y of the rotor reaches the slot 7,

that is, when 'the coil. 8 occupies the position indicated at III, thechange in the total flux interlinked with th'e coil -8 becomes larger, and, being still of the same direction, a negativevoltage of larger, magnitude is induced in the coil 8. For the remainder of the cycle the change in the total. flux interlinked with the coil 8 is uniform, whereby a constant negative voltage is. induced .in the coil until the forward tip. of section X of the rotor is suddenly increased and reversed in elt'ect resulting in the generation in the coil 8 of the maximum positive voltage. In Fig. 4 of the drawings I haveillustrate by curve C a voltage wave form obtained by the commutator method for obtaining an electromotive force of special wave form as described hereinbefore. Curve D of this figure represents an oscillogram of the voltage obtained by a dynamo-electric machine constructed in accordance with the principle of my invention. The actual voltage curve 1), as indicated by the oscillogram, is in every respect an entirely satisfactory approximation of the desired electromotiv'e force of special wave form, as indicated by the curve (1. i

I have explained my invention by illustratiug and describing a particular embodi- .meut llI(l(.()f,.llllt it will be readily understood by those skilled in the art that the iiivention may be embodied in many other forms than that shown and described. I, ac

cordingly, do not wish to be restricted to the setting forth my invention in accordance with the patent statutes. The terms of the appended claims, therefore, are not restricted to the precise structure disclosed, but are intended to cover all changes and modifications within the spirit and sco e of my in-, vention, and it will hence be un erstood that my invention may be embodied in practice in various other ways than that herein illustrated and described and still be within the purview of the claims appended hereto.

What I claim as' new and desire to secure by Letters Patent of the United States, is; 1. An apparatus for producing an alter natiug electroinotive force of unsymmetrical wave form comprising a stator of magnetic material having two spaced slots on its inner periphery, an electric current conductive coil positioned in-said slots, an' exciting coil adapted to develop a. magnetic field to which said first coil is subjected, and a rotor ofn'iagnetic material having its periphery divided into three sections each section being of gradually varying radial width, one of said sections being of greater cireumferen tial width than' either of the other two sections.

:2. An apparatus for producing an alternatiug electi'omotive forceof unsymmetrb.

cal wave form comprising stator of mag-' netie material having two spaced slots on-its inner periphery, an electric current condur/ tive coil positioned'in said slots, an exciting 'coil adaptedto" develop a magnetic field to which said first coilis subjected, and a' rotor having its peripheral surface divided into a three sections-each section being of gradupresent opposite saidcoil a peripheral surface whose radial width abruptly increases from a minimum value to a maximum value all by alternate gradualand abruptchanges.

Inwit 'icss whereof I have hereunto set my hand this 21st dayof August,'1914.

' a ERNST F. W. ALEXANDERSON- Witnesses:

Remains B. HULL, I'IELEN ORFORD.

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C O 3% ib O Q It is hereby certified that in Letters Patent No. 1,250,752, granted December 18, 1917, upon the application of Ernst F. W. Alexender'son, of Schenectady, New York, for an improvement in "Apparatus for Producing an Electromotive Force of Special Wave Form, an error appears in the printed specification requiring correction as follows: Page 3, line 120, claim 3, after the word changes insert the clause and means for developing a flux in said magnetic circuit; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 12th day of February, A. D., 1918.

[SEAL] J. T. NEWTON,

Commissimwr 0/ PGHWLLS. 

